This invention relates generally to loose-leaf binder mechanism of the type which are commonly used in ring binders.
Ring binders include an elongated housing containing a pair of pivoting elongated hinge plates each of which carries a series of spaced apart prongs. Each prong on one hinge plate is aligned with a prong on the other hinge plate. The hinge plate may be pivoted relative to each other between two positions. In one of these positions the aligned prongs engage each other to form a closed loose-leaf sheet retaining loop; and in the other position each pair of aligned prongs is spread apart to permit removal or insertion of loose-leaf sheets. While the prongs can be used as levers to move the hinge plates between the two positions, such binders commonly include separate lever-type actuating means for pivoting the hinge plates between the open and closed position as exemplified in the U.S. Pat. Nos.
1,787,956, 1,841,793, 1,868,793, 1,896,838, 1,896,839, 1,913,700, 1,927,113, 2,013,552 2,041,168, 2,498,902, 3,101,719, and 3,884,586.
One problem associated with loose-leaf binders of the type described is the possibility that the prongs may be accidentally opened during use. This may happen, for example, if one drops a filled binder causing the hinge plates to open. In situations where the binder is stored in an inverted position with the loose-leaf sheets suspended or hanging from the loop defined by the closed prongs, the weight of the loose-leaf sheets may tend to pry the prongs apart, and in some housings may even cause complete opening of the prongs. To prevent accidental or otherwise unintentional opening of the prongs, a means for locking the prongs in closed position is required. Many known loose-leaf ring binders have been constructed with various forms of locking means as exemplified by the U.S. Pat. Nos. 2,061,676, 2,105,235, 2,950,719, 3,077,388, 3,098,490 and 3,884,586. The most pertinent of these, relative to this invention, is U.S. Pat. No. 3,098,490 which provides a construction where a portion of an actuating lever is wedged between the hinge plates and the housing to lock the prongs together.